1. Field of the Invention
This invention relates generally to improvements in electroplating cells and, more particularly, but not by way of limitation, to an improved electroplating cell having a plurality of vane sections extending substantially radially therefrom at spaced intervals along the length thereof for inducing turbulence in the boundary layer adjacent the cathode.
2. Prior Art Statement
In the electroplating art, it is well known that certain metal ions in solution can be deposited on a negatively-charged surface, commonly referred to as a cathode. For example, in U.S. Pat. No. 2,791,555, issued to Duisenberg et al., it is taught that silver ions can be extracted from used photographic or "hypo" solutions via a plurality of disc-shaped cathodes which are negatively biased relative to a plurality of anode elements. Variations of the disc structure can be seen in the following U.S. Pat. Nos.: 3,342,718, issued to Adams; 3,458,425, issued to Tolle et al.; 3,964,990, issued to Woyden; and 4,049,512, issued to Tolle, Jr.
During the electroplating process, it is well known that a consistent rate of deposition of the metal ions may best be achieved by circulating the metal ion solution past the cathode, thereby replacing the metal ions already plated out on the cathode. In U.S. Pat. Nos. 3,003,942, issued to Cedrone, and 3,964,990, issued to Woyden, pumps are employed to induce the desired fluid circulation. In U.S. Pat. No. 4,049,512, issued to Tolle, Jr., the disc-type cathodes referred to above are provided with impeller surfaces to induce the desired fluid circulation. On the other hand, a plurality of rotating agitators are employed in U.S. Pat. No. 3,477,926, issued to Snow et al. Variations of the agitator structure can be seen in the following U.S. Pat. Nos.: 3,583,897, issued to Fulweiler; 3,806,434, issued to Goold et al.; and U.S. Pat. No. 4,018,658, issued to Alfin et al.
In U.S. Pat. No. 3,715,299, issued to Anderson et al., it is recognized that continuous disturbance of the boundary layer surrounding the cathode structure significantly improves the electroplating process, while discouraging the formation of deleterious by-products. However, the stationary boundary layer trippers proposed therein must extend into close proximity with the cathode surface, thereby limiting the thickness of the deposition layer, as well as discouraging the circulation of solution between the cathode and the trippers. In contrast, the helical vanes taught in U.S. Pat. No. 3,560,366, issued to Fisher induce the desired circulation between the cathode and anode, but are incapable of creating the desired turbulence in the boundary layer. In U.S. Pat. No. 3,551,317, issued to Cooley, it is proposed to solve the boundary layer problem by continually stripping and replacing the entire mass of solution interposed between the anode and cathode.
Other electrolysis apparatus of general interest can be seen in U.S. Pat. Nos. 2,536,912, issued to Corbett, and 2,867,560, issued to Dufour et al.